ORCID Profile
0000-0001-8277-8614
Current Organisation
The University of Hong Kong
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Publisher: Elsevier BV
Date: 09-2020
Publisher: Wiley
Date: 17-07-2020
DOI: 10.1111/COBI.13520
Publisher: MDPI AG
Date: 22-05-2021
DOI: 10.3390/RS13112047
Abstract: Anthropogenic and natural disturbances can cause degradation of ecosystems, reducing their capacity to sustain bio ersity and provide ecosystem services. Understanding the extent of ecosystem degradation is critical for estimating risks to ecosystems, yet there are few existing methods to map degradation at the ecosystem scale and none using freely available satellite data for mangrove ecosystems. In this study, we developed a quantitative classification model of mangrove ecosystem degradation using freely available earth observation data. Crucially, a conceptual model of mangrove ecosystem degradation was established to identify suitable remote sensing variables that support the quantitative classification model, bridging the gap between satellite-derived variables and ecosystem degradation with explicit ecological links. We applied our degradation model to two case-studies, the mangroves of Rakhine State, Myanmar, which are severely threatened by anthropogenic disturbances, and Shark River within the Everglades National Park, USA, which is periodically disturbed by severe tropical storms. Our model suggested that 40% (597 km2) of the extent of mangroves in Rakhine showed evidence of degradation. In the Everglades, the model suggested that the extent of degraded mangrove forest increased from 5.1% to 97.4% following the Category 4 Hurricane Irma in 2017. Quantitative accuracy assessments indicated the model achieved overall accuracies of 77.6% and 79.1% for the Rakhine and the Everglades, respectively. We highlight that using an ecological conceptual model as the basis for building quantitative classification models to estimate the extent of ecosystem degradation ensures the ecological relevance of the classification models. Our developed method enables researchers to move beyond only mapping ecosystem distribution to condition and degradation as well. These results can help support ecosystem risk assessments, natural capital accounting, and restoration planning and provide quantitative estimates of ecosystem degradation for new global bio ersity targets.
Publisher: Wiley
Date: 30-11-2023
DOI: 10.1002/LDR.4492
Abstract: Landslides are common in tropical and subtropical regions with hilly terrains and heavy rainstorms, and can cause significant economic, ecological, and social impacts. Natural forest succession is usually slow on landslides due to poor soil structure and lack of woody plant seeds, and often comes with a higher risk of repeated landslides. Active forest restoration has been increasingly suggested as an effective alternative to restore exposed landslide scars. Here, we evaluated the effectiveness of using different seed coatings and surface soil treatments on seed germination and seedling establishment of pioneer and late‐successional tree species on landslide scars in Hong Kong. Our results show that biochar‐dominant seed coating boosted seed germination rate by an additional 9.33% (Standard error = 0.04), while clay‐dominant seed coating did not show significant effects. The effects on seedling survival were not significant in both seed coating and surface soil treatments. Our results also show that large seed and later successional species have significantly higher germination rates than pioneer species and are able to successfully establish on landslide sites. These results suggest that direct seeding using a biochar seed coat with large seeds or late‐successional species is a useful method to enhance tree seed germination—an essential first step to restore the forests after landslide disturbances, with potential to be extended to other humid tropical and subtropical forests.
Publisher: California Digital Library (CDL)
Date: 30-12-2019
DOI: 10.21425/F5FBG42455
Publisher: Wiley
Date: 03-05-2022
DOI: 10.1111/GEB.13499
Abstract: ‘Megafire’ is an emerging concept commonly used to describe fires that are extreme in terms of size, behaviour, and/or impacts, but the term’s meaning remains ambiguous. We sought to resolve ambiguity surrounding the meaning of ‘megafire’ by conducting a structured review of the use and definition of the term in several languages in the peer‐reviewed scientific literature. We collated definitions and descriptions of megafire and identified criteria frequently invoked to define megafire. We recorded the size and location of megafires and mapped them to reveal global variation in the size of fires described as megafires. We identified 109 studies that define the term ‘megafire’ or identify a megafire, with the term first appearing in the peer‐reviewed literature in 2005. Seventy‐one (~65%) of these studies attempted to describe or define the term. There was considerable variability in the criteria used to define megafire, although definitions of megafire based on fire size were most common. Megafire size thresholds varied geographically from 100–100,000 ha, with fires 10,000 ha the most common size threshold (41%, 18/44 studies). Definitions of megafire were most common from studies led by authors from North America (52%, 37/71). We recorded 137 instances from 84 studies where fires were reported as megafires, the vast majority (94%, 129/137) of which exceed 10,000 ha in size. Megafires occurred in a range of biomes, but were most frequently described in forested biomes (112/137, 82%), and usually described single ignition fires (59% 81/137). As Earth’s climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we suggest a definition of megafire as fires 10,000 ha arising from single or multiple related ignition events. We introduce two additional terms – gigafire ( 100,000 ha) and terafire ( 1,000,000 ha) – for fires of an even larger scale than megafires.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 03-2022
Publisher: Wiley
Date: 31-01-2019
DOI: 10.1111/ECOG.04143
Publisher: Elsevier BV
Date: 03-2023
Publisher: Springer Science and Business Media LLC
Date: 30-05-2019
Publisher: Wiley
Date: 24-05-2018
DOI: 10.1111/CONL.12372
Publisher: Elsevier BV
Date: 12-2022
Publisher: Wiley
Date: 10-12-2022
DOI: 10.1111/NPH.18632
Abstract: To what degree plant ecosystems thermoregulate their canopy temperature ( T c ) is critical to assess ecosystems' metabolisms and resilience with climate change, but remains controversial, with opinions from no to moderate thermoregulation capability. With global datasets of T c , air temperature ( T a ), and other environmental and biotic variables from FLUXNET and satellites, we tested the ‘limited homeothermy’ hypothesis (indicated by T c & T a regression slope 1 or T c T a around midday) across global extratropics, including temporal and spatial dimensions. Across daily to weekly and monthly timescales, over 80% of sites/ecosystems have slopes ≥1 or T c T a around midday, rejecting the above hypothesis. For those sites unsupporting the hypothesis, their T c – T a difference (Δ T ) exhibits considerable seasonality that shows negative, partial correlations with leaf area index, implying a certain degree of thermoregulation capability. Spatially, site‐mean Δ T exhibits larger variations than the slope indicator, suggesting Δ T is a more sensitive indicator for detecting thermoregulatory differences across biomes. Furthermore, this large spatial‐wide Δ T variation (0–6°C) is primarily explained by environmental variables (38%) and secondarily by biotic factors (15%). These results demonstrate erse thermoregulation patterns across global extratropics, with most ecosystems negating the ‘limited homeothermy’ hypothesis, but their thermoregulation still occurs, implying that slope 1 or T c T a are not necessary conditions for plant thermoregulation.
Publisher: Elsevier BV
Date: 10-2022
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Calvin Lee.